The present invention relates generally to a method and apparatus for improving the vision of an eye, and, more particularly concerns a method and apparatus that improve vision at all distances, hereafter referred to as “universal improvement.”
Most common defects in human vision are caused by the inability of the eye to focus incoming light to a common focal point on the retina. For example, nearsightedness can be attributed to an eye which focuses light anterior to the retina, farsightedness can be attributed to an eye which focuses incoming light posterior to the retina, and astigmatism can be attributed to an eye which does not have a common focal point. Human optical scientists frequently model the cornea as a portion of an ellipsoid defined by orthogonal major and minor axes.
Today, vision is commonly improved in one of two ways: either a lens is placed in front of the eye (e.g. a contact lens or a spectacle lens) or within the eye (e.g. an intraocular lens) to refocus incident light into the eye appropriately. Alternatively, the effective external surface shape of the cornea is changed, as by laser ablation surgery or other surgical means to alter the anterior surface shape of the cornea. Such surgical procedures for correcting visual acuity are typically directed at increasing or decreasing the surface curvature of the cornea. Some procedures are intended to make the corneal shape more spherical, and others are intended to change the corneal shape to an “average” ellipse, or more recently to making corrections based on wavefront analysis, a methodology that is intended to correct for the “higher order aberrations” of the eye.
Contact lenses or spectacles are used to provide vision correction for objects of regard at different distances from the eye, for example objects relatively close to the eye or for objects remotely displaced from the eye. In this regard, different zones of a lens have been provided with different lens powers so as to permit the wearer to see objects at different distances. The traditional “multifocal” contact lens is one wherein there are power differences located in different areas or zones on the surface of the lens. Such zones have been designed as spherical segments and spherical lunes of different power formed on the lens. Although such lenses have provided vision correction at certain distances, they have not provided sufficient universal vision improvement to restore natural visual acuity for an eye that requires multiple levels of depth correction in addition to the distance refractive error. In addition, variable focus spectacle lenses have been provided in which a central optical region is formed with a curvature that varies continuously with vertical position, to provide vision correction at all distances. However, the wearer must raise or lower his head to make an adjustment for distance. Some contact lens designs provide two or more zones of refractive power in distinct bands on the anterior surface. This lens translates in position depending on lid position. In order to provide clear vision with the translating design, the wearer must, similarly, raise or lower his head in order to adjust for the distance of the object being viewed. It is less than optimal to require the wearer to make such adjustments.
It would be desirable to provide universal vision improvement without the need for any extraneous physical movements by the wearer.